The research study utilizes in vitro system which includes corneal epithelium and trigeminal neurons. While the system was developed during preliminary studies, the investigators are now refining the culture methods. Morphological and physiological characteristics of the co-cultured cells will be studied especially as they compare with each cell type cultured separately. Trophic interactions between the tissues may thus be revealed. This "control" data will be used in subsequent phases of their study which utilize the co-culture system to address questions of clinical concern. Since Herpes simplex virus (HSV) is the leading infectious cause of corneal blindness and visual impairment in the U.S., there is considerable interest in understanding its interaction with the corneal epithelium and its trigeminal innervation as well as how to prevent those interactions. During the course of this project, the effect of selected strains of HSV-1 on the corneal epithelium alone or in co-culture with the trigeminal neurons will be studied extensively. The presence of viral antigen in the cultures will be determined by plaque assay and immunohistochemical procedures. Morphological characterization will use standard methods of phase and electron microscopy. Electrophysiology characterization will involve intracellular measurements of active membrane properties of both the trigeminal neurons and corneal epithelial cells.